1. Field of the Invention
The present invention relates to a fuel supply control system for an internal combustion engine, and more particularly to a fuel supply control system having a fuel supply cut-off function operable upon deceleration of the engine.
2. Description of the Prior Art
Electronically controlled fuel injection systems fall into either one of two categories; (a) a type employing a plurality of fuel injection valves respectively for each of cylinders, and (b) a type employing a single fuel injection valve which is located immediately downstream of the throttle valve, for example.
In the above system in order to improve fuel economy, it has been proposed to provide a fuel cut-off function which temporarily terminates the supply of fuel during periods when engine torque is not required, such as during deceleration. However, in the case of a single point injection system, this cut-off function has induced a problem that the walls of the induction passage or conduit between the injector and the cylinders become wet with fuel during normal operation and this fuel is substantially removed by the air passing therethrough during the fuel cut-off. Thus, upon resumption of fuel injection, a substantial amount of the fuel initially injected impinges on the now dry induction passage walls to re-wet same. Accordingly a substantial delay results between the resumption of injection and desired amount of fuel actually being delivered to the engine cylinders giving rise to poor air-fuel ratio control.